By NIK NORIMAN BIN ZULKEPLI - Universiti Sains Malaysiaeprints.usm.my/29695/1/Characterization_and_properties_of... · 2016. 2. 17. · NIK NORIMAN BIN ZULKEPLI Thesis submitted in

CHARACTERIZATION AND PROPERTIES OF STYRENE BUTADIENE RUBBER/RECYCLED ACRYLONITRILE

B1JTADIENE RUBBER (SBR!NBRr) BLENDS

By

NIK NORIMAN BIN ZULKEPLI

Thesis submitted in fulfilment of the requirements for the degree of

Doctor of Philosophy

February 20 11

DEDICATION

Mami, Papa, Niza and family

ACKNOWLEDGEMENTS

Bismillaahirrahmaanirrahiim,

A special acknowledgement to Universiti Malaysia Perlis and Ministry of

Higher Education (MOHE) for the scholarship to undertake this study.

First of all, I am heartily thankful to my supervisor, Professor Dr Hanafi Bin

Ismail, whose encouragement, guidance and support from the initial to the final level

enabled me to develop an understanding of the study. Compassionately that he was

always there to listen, patiently, giving advice and showed me different ways to

approach a research problem and the need to be persistent to accomplish any goal. In

addition, the remembrance as a first champion in P/Grad Super Series on your

trophy will be remaining in my days. I also wish to express my appreciation to my

second supervisor, Dr Azura Abd Rashid, who made many valuable suggestions and

gave constructive advice to improve the quality of this thesis.

Special gratitude are due to Professor Dr Ahmad Fauzi Bin Mohd Noor,

Dean and all the technical staff in School of Materials and Mineral Resources

Engineering for taking intense academic interest in this study as well as providing

valuable suggestions. My utmost appreciation goes to Mr Segar, Mr Rokman, Mr

Che Mat Hassan, Mr Rashid, Mr Azam, Mr Faizal, Mr Shahril, Mr Khairi, Mr Halim

and Mr Mokhtar for their valuable assistance in the field. Without their help, the

research would not have been accomplished in time. I would alos like to show my

appreciation to Universiti Sains Malaysia for awarding me the short term grant

(USM-RU-PGRS) which has supported me during my three years of research.

II

I am indebted to my many student colleagues especially Sung Ting, Yamuna,

Razif, Basri, Ragu, Kahar, Hamid, Faizal, Firdaus Lendu, Zunaida, Jai, Firdaus, Nik

Akmal, Zharif and Mat Shah for providing a stimulating and fun environment in

which to learn and grow. I would like to express special thanks to Niza for her

motivation, encouragement and assistance during completion of this thesis.

Most importantly, my special appreciation goes to my parents, Zulkepli bin

Hj Abd Hamid and Nik Khairani Binti Mohamad. This is the best honour to show

my gratitude thus I dedicate this thesis for them. Above all, I wish to thank my entire

family for their patient, encouragement and understanding along my study.

Lastly, it is a pleasure to thank those who made this thesis possible. I offer

my regards and blessings to all of those who supported me in any respect during the

completion of the thesis .

. ~....: •

iman Bin Zulkepli

February 2011

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LIST OF CONTENTS

DEDICATION ACKNOWLEDGEMENT LIST OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF SYMBOLS LIST OF ABBREVIATIONS ABSTRAK ABSTRACT

CHAPTER 1: INTRODUCTION 1.1 Recycling of Waste Rubber

1.1.1 An outlook and trend 1.1.2 Malaysia as rubber manufacturer 1.1.3 Utilization

1.2 Research Background 1.3 Problem Statement 1.4 Research Objectives

CHAPTER 2: LITERATURE REVIEW 2.1 Recycled Rubber Waste: An Approach and Utilization

2.1.1 A terminology used for recycling 2.1.2 Grindings and powdered recycled rubber 2.1.3 Properties of recycled rubber blends based on study case

2.1.3.1 The influence on rheology 2.1.3.2 The influence on curing characteristics 2.1.3.3 The influence on mechanical properties

2.1.4 Acrylonitrile butadiene rubber (NBRr) glove 2.1.5 Synthetic rubber

2.1.5.1 Styrene butadiene rubber (SBR) 2.1.5.2 Acrylonitrile butadiene rubber (NBR)

2.1.6 The SBRINBR blends 2.1. 7 Compounding of recycled material

2.2 Compatibilization of Rubber Blends 2.2.1 Introduction 2.2.2 Method of compatibilization 2.2.3 Epoxidized natural rubber (ENR-50) 2.2.4 Trans-polyoctylene rubber (TOR)NESTENAMER

-High performance polymer 2.2.4.1 Introduction 2.2.4.2 Synthesis and structure oftrans-polyoctylene rubber

(TOR) 2.2.4.3 The unique and exceptional properties of TOR are

characterized by four structural features 2.2.4.4 TOR in many applications

2.3 Filler Reinforcement in Rubber Blend 2.3.1 Introduction

IV

11

iv ix xii

XXV xxvi xxvii XXlX

1 2 4 6 9 12

13 15 17

18 19 20 22

24 25 26 27

28 29 30

34 36

37

39

42

2.4

2.5

2.3.2 Carbon black 43 2.3.3 Silica 43 2.3.4 Interaction filler and elastomers

2.3.4.1 Filler particle size 46 2.3.4.2 Filler surface characteristics 47 2.3.4.3 Interaction between the surfaces of the filler and the 47

matrix based on model 2.3.4.4 Silane coupling agents

Degradation on Polymer 2.4.1 Introduction 2.4.2 Natural weathering on rubber

2.4.2.1 The approach, factors and basic 2.4.1.2 Secondary factors of natural weathering 2.4.1.3 Mechanism of oxidative degradation 2.4.1.4 Mechanism of ozone attack

Current Commercial Applications of Recycled Rubber Products 2.5.1 Introduction 2.5.2 Rubber roofing shingles 2.5.3 Recycled rubber in innovative rubber flooring products

50

52

53 59 60 62

63 63 65

CHAPTER3:EXPERIMENTALPROCEDURES 3.1 Introduction 67 3.2 Materials

3.2.1 Styrene Butadiene Rubber (SBR) 67 3.2.2 Acrylonitrile Butadiene Rubber (NBR) 68 3.2.3 Recycled Acrylonitrile Butadiene Rubber (NBRr) 68 3.2.4 Carbon Black 69 3.2.5 Ingredients for vulcanizations/coagents 70 3.2.6 Epoxidized Natural Rubber (ENR-50) as compatibilizer 70 3.2.7 Trans Polyoctylene Rubber (TOR) as compatibilizer 70 3.2.8 Silica (Vulcasil S) 71

3.3 Equipments 3.3.1 Grinder 71 3.3.2 Particle size analysis 71 3.3.3 Two-roll mill 72 3.3.4 Hot-Press 72

3.4 The Blends Preparation and Formulations 3.4.1 The SBR/NBRv (virgin) blends and SBRINBRr (recycled) 72

blends 3.4.2 The SBRINBRr blends with different recycled NBR size 73 3.4.3 The SBR/NBRr blends with Trans-Polyoctylene Rubber 73

(TOR) as compatibilizer 3.4.4 The SBRINBRr blends with epoxidize natural rubber (ENR- 74

50) as compatibilizer 3.4.5 The SBRINBRr blends with carbon black/silica (CB/Sil) 75

hybrid fillers 3.4.6 Mixing and compounding 76 3.4.7 Curing characteristics 77 3.4.8 Vulcanization 78

v

3.5 Properties of Rubber Blends 3.5.1 Mechanical and physical properties of rubber blends

3.5.1.1 Tensile Strength 3.5 .1.2 Crosslinked Density 3.5.1.3 Hardness 3. 5 .1. 4 Resillience 3.5.1.5 Fatigue life

3.5.2 Morphology Studies (scanning electron microscopy) 3.5.3 Thermal Analysis

3.5.3.1 Thermogravimetric Analysis (TGA) 3.5.3.2 Differential Scanning Calorimetry (DSC)

3.5.4 Fourier Transform Infrared (FTIR) 3.5.5 Weathering Test

3.5.5.1 Weathering parameters 3.6 Experimental Chart

CHAPTER 4: CHARACTERIZATION OF RECYCLED ACRYLONITRILE BUTADIENE RUBBER (NBRr) GLOVE

78 79 80 80 80 81

81 82 82 82 83 88

4.1 Particle Size Distribution 89 4.2 Scanning Electron Microscopy and Image Analyser Observations 89 4.3 Fourier Transform Infrared (FTIR) 92

CHAPTER 5: COMPARISON OF PROPERTIES OF STYRENE BUTADIENE RUBBER/VIRGIN ACRYLONITRILE-BUTADIENE RUBBER (SBRINBRv) WITH STYRENE BUTADIENE RUBBER/RECYCLED ACRYLONITRILE-BUTADIENE RUBBER (SBRINBRR) 5.1 Introduction 93 5.2 Curing Characteristics 94 5.3 Mechanical and Physical Properties 97 5.4 Morphology Studies (scanning electron microscopy) 103 5.5 Fourier Transform Infrared (FTIR) 105 5.6 Thermal Analysis

5.6.1 Thermogravimetric Analysis (TGA) 108 5.6.2 Differential Scanning Calorimetry (DSC) 110

CHAPTER 6: THE EFFECTS OF DIFFERENT PARTICLES SIZE OF RECYCLED ACRYLONITRILE-BUTADIENE RUBBER (SBRINBRR) AND IT'S BLEND RATIO ON STYRENE BUTADIENE RUBBER/RECYCLED ACRYLONITRILE-BUTADIENE RUBBER (SBRINBRR) 6.1 Introduction 113 6.2 Curing Characteristics 114 6.3 Mechanical and Physical Properties 116 6.4 Morphology Studies (scanning electron microscopy) 122 6.5 Fourier Transform Infrared (FTIR) 126 6.6 Thermal Analysis


VI

CHAPTER 7: THE EFFECTS OF TRANS POLYOCTYLENE RUBBER (TOR) AS A COMPATIBILIZER ON STYRENE BUTADIENE RUBBER/RECYCLED ACRYLONITRILEBUTADIENE RUBBER (SBRINBRR) BLENDS 7.1 Introduction 133 7.2 Curing Characteristics 134 7.3 Mechanical and Physical Properties 135 7.4 Morphology Studies (scanning electron microscopy) 143 7.5 Fourier Transform Infrared (FTIR) 147 7.6 Thermal Analysis


CHAPTER 8: THE EFFECTS OF EPOXIDIZED NATURAL RUBBER (ENR-50) AS A COMPATIBILIZER ON STYRENE BUTADIENE RUBBER/RECYCLED ACRYLONITRILEBUTADIENE RUBBER (SBRINBRR) BLENDS 8.1 Introduction 154 8.2 Curing Characteristics 155 8.3 Mechanical and Physical Properties 156 8.4 Morphology Studies (scann.ing electron microscopy) 163 8.5 Fourier Transform Infrared (FTIR) 167 8.6 Thermal Analysis


CHAPTER 9: THE EFFECTS OF CARBON BLACK/SILICA (CB/SIL) HYBRID FILLER IN PRESENCE OF SILANE COUPLING AGENTS (SI69) FILLED STYRENE BUTADIENE RUBBER/RECYCLED ACRYLONITRILE-BUTADIENE RUBBER (SBRINBRR) BLENDS 9.1 Introduction 17 5 9.2 Curing Characteristics 176 9.3 Mechanical and Physical Properties 180 9.4 Morphology Studies (scanning electron microscopy) 188 9.5 Fourier Transform Infrared (FTIR) 193 9.6 Thermal Analysis

9.6.1 Thermogravimetric Analysis (TGA) 195 9 .6.2 Differential Scanning Calorimetry (DSC) 198

CHAPTER 10: NATURAL WEATHERING TEST OF STYRENE BUTADIENE RUBBER/VIRGIN ACRYLONITRILE-BUTADIENE RUBBER (SBRINBRv) AND STYRENE BUTADIENE RUBBER/RECYCLED ACRYLONITRILE-BUTADIENE RUBBER (SBRINBRr) BLENDS 10.1 Introduction 201 10.2 The effects on natural weathering test of styrene butadiene

rubber/virgin acrylonitrile butadiene rubber (SBR/NBRv) blends

VII

and styrene butadiene rubber/recycled acrylonitrile butadiene rubber (SBRINBRr) blends. 1 0.2.1 Tensile Retention 203 1 0.2.2 Morphology 208

10.3 The effects on natural weathering test of different size of styrene butadiene rubber/recycled acrylonitrile butadiene rubber (SBRINBRr) blends. 10.3.1 Tensile Retention 212 10.3.2 Morphology 218

10.4 The effects on natural weathering of styrene butadiene rubber/recycled acrylonitrile butadiene rubber (SBRINBRr) blends with trans polyoctylene rubber (TOR) as a compatibilizer 1 0.4.1 Tensile Retention 223 1 0.4.2 Morphology 228

10.5 The effects on natural weathering test of styrene butadiene rubber/recycled acrylonitrile butadiene rubber (SBRINBRr) blends with epoxidized natural rubber (ENR-50) as a compatibilizer 10.5.1 Tensile Retention 231 10.5.2 Morphology 236

10.6 The effects on natural weathering test of CB/Sil hybrid fillers filled SBR/NBRr blends with and without Si69 1 0.6.1 Tensile Retention 10.6.2 Morphology

CHAPTER 11: CONCLUSIONS AND SUGGESTIONS 11.1 Conclusions 11.2 Suggestions for further studies

REFERENCES

APPENDIXES Appendix A: List of Journal's title Appendix B: List of Conference's title

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239 244

250 251

253

273 275

LIST OF TABLES

PAGE

Table 1.1 Statistical summary of world synthetic rubber 3

Table 1.2 Synthetic rubber price 3

Table 1.3 Malaysia's Export of Selected Rubber Products, 2005- 4 2008

Table 1.4 Bond Strength of Different Bonds in Rubber Network 10

Table 2.1 Effect of powdered rubber (abraded) loading on the 21 mechanical properties of powdered rubber-filled vulcanizates a,b

Table 2.2 Properties ofNR Vulcanizates Containing 30 Phr of GRTa 22

Table 2.3 Table qualitative summary of effect of 26 acrylonitrile/butadiene ratio upon properties of acrylonitrile-butadiene rubbers

Table 2.4 Typical properties of ENR 32

Table 2.5 Physical properties of ENR vulcanizatcs 32

Table 2.6 Potential commercial uses of ENR 33

Table 2.7 Physical and chemical properties of Vestanamer 8012 and 37 6213

Table 3.1 Typical data of the styrene butadiene rubber (SBR), 1502 67

Table 3.2 Typical properties of acrylonitrile butadiene rubber (NBR), 68 DN 3350

Table 3.3 Some of ingredients ofNBRr glove obtained from 69 manufacturer

Table 3.4 The grade of carbon black, N330 69

Table 3.5 The characteristics of the materials 70

Table 3.6 The typical properties of ENR-50 70

Table 3.7 The technical specification of trans-polyoctylene rubber 71 (TOR) (V8012)

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Table 3.8 Typical properties of silica (vulcasil S) 71

Table 3.9 The formulation of SBR/NBRv blends and SBRINBRr 73 blends

Table 3.10 The formulation of SBR/NBRr blends with different size of 73 NBRr

Table 3.11 The formulation of SBRINBRr blends with TOR as 74 compatibilizer

Table 3.12 The formulation of SBRINBRr blends with ENR-50 as 75 compatibilizer

Table 3.13 The formulation of SBRINBRr blends with carbon 75 black/silica (CB/Sil) hybrid filler

Table 3.14 The mixing procedures and time 76

Table 3.15 Type weathering tests and time range 83

Table 5.1 The curing characteristics of SBR/NBRv versus SBR/NBRr 96 blends

Table 5.2 Experimental data ofTG and DTG ofSBR/NBRv (R05), 110 SBRINBRr (R05), SBRINBRv (R15), SBRINBRr (R15), SBR/NBRv (R50) and SBR/NBRr (R50) blends

Table 5.3 Experimental data ofDSC thermograms ofSBR/NBRv 112 (R05), SBRINBRr (R05), SBR/NBRv (R15), SBR/NBRr (R15), SBR/NBRv (R50) and SBRINBRr (R50) blends

Table 6.1 The effects of different size ofNBRr and blend ratio on 115 curing characteristics of SBR/NBRr blends

Table 6.2 Experimental data ofTG and DTG ofSBR/NBRr R05 (S1), 130 SBR/NBRr R05 (S2), SBRINBRr R05 (S3), SBR/NBRr R50 (S1), SBR/NBRr R50 (S2) and SBR/NBRr R50 (S3) blends

Table 6.3 Experimental data of DSC thermogram of SBRINBRr 132 blends ofNBRr ranging from 124- 334 Jlm (S1), 0.85 -15.0 mm (S2) and 10 -19 em (S3) at 95/5 (R05) and 50/50 (R50) blends ratio

Table 7.1 Cure characteristics of SBR/NBRr blends with and without 136 TOR

Table 7.2 Experimental data of TGA and DTGA of SBRINBRr/TOR 151

X

(R05/TOR), SBR/NBRr/TOR (R50/TOR), SBRINBRr (ROS) and SBRINBRr

Table 7.3 Crystallization temperature of SBR, NBRr, 153 R05,SBRINBRr/TOR(R05/TOR), SBR/NBRr (R50) and SBRINBRr/TOR (RSO/TOR)

Table 8.1 Cure characteristics of SBR/NBRr blends with and without 157 ENR-50

Table 8.2 Experimental data ofTG /DTG ofR05 ENR-50, R50 ENR- 172 50, ROS and RSO

Table 8.3 Crystallization temperature of SBR, NBRr, ROS, R50, 173 ROS/ENR-50 and RSO/ENR-50

Table 9.1 Cure characteristics of CB/Sil hybrid fillers filled 179 SBRINBRr blends with and without Si69

Table 9.2 Experimental data of TG and DTG of CB/Sil ( 40/1 0), 198 CB/Sil (30/20), CB/Sil (1 0/40), CB/Sil (1 0/40), CB/Sil/Si69 (40/10), CB/Sil/Si69 (30/20) and CB/Sil/Si69 (10/40) hybrid filler filled SBR/NBRr blends

Table 9.3 Experimental data of DSC thermogram of CB/Sil ( 40/1 0), 200 CB/Sil (30/20), CB/Sil (10/40), CB/Sil (10/40), CB/Sil/Si69 (40/10), CB/Sil/Si69 (30/20) and CB/Sil/Si69 (10/40) hybrid filler filled SBR/NBRr blends

XI

LIST OF FIGURES

PAGE

Figure 1.1 Rubber gloves are processed into reclaimed rubber at the 5 Rubplast factory

Figure 2.1 The summary of reclaiming of rubbers by physical and 16 chemical processes

Figure 2.2 llustrates (a) the ultra-fine powdered rubber(< 10m) exists 18 as aggregates which break down under shear (b) a typical abraded particle separated out by the ultrasonic dispersion technique

Figure 2.3 (a) Structure of natural rubber, cis-1, 4-polyisoprene, 31 (b) formation of peroxy formic acid and (c) the production of ENR

Figure 2.4 Trans-polyoctylene rubber (TOR) synthesis in 36 scemetically

Figure 2.5 Addition of TORIVESTENAMER to ground tire rubber 41 (GTR)

Figure 2.6 Surface chemistry of carbon blacks and silicas 44

Figure 2.7 Classification of fillers according to average particle size 46

Figure 2.8 Relevant dimensions in rubber-filler interactions 47

Figure 2.9 Schematic models of morphological transformations in 48 filled polymers, occurring as the silica content increases from less than 10 wt% (a), to ca. 10 wt% (b), to over 20 wt% (c), to over 50 wt% (d). The line-shaded areas are the silica particles, while the black areas correspond to tightly bound polymer and the gray areas to loosely bound polymer

Figure 2.10 The concept of segmental interaction with a carbon black 49 surface

Figure 2.11 The chemical structure of Si69 50

Figure 2.12 The formation of chemical bonds between the filler and 51 rubber through the silane

Figure 2.13 Different pathways of degradation and stabilization 52

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Figure 2.14 A schematic diagram outlining the main test variables 55

Figure 2.15 Summary of common responses of materials towards 56 weathering

Figure 2.16 The basics principles of the mechanism of the oxidative 61 degradation of rubber

Figure 2.17 Possible inhibition reactions where AH is an inhibitor 61

Figure 2.18 Mechanism of ozone attacks on rubber 62

Figure 2.19 Rubber roofing shingles 64

Figure 2.20 Rephouse's commercial rubber flooring 66

Figure 3.1 NBRr glove obtained from manufacture 68

Figure 3.2 Weather parameters throughout 1st weathering test (Jun 84 2007 l.rntil December 2007) (i) mean rainfall and relative humidity (ii) mean minimum and maximum temperature

Figure 3.3 Weather parameters throughout 2st weathering test 85 (January 2008 until July 2008) (i) mean rainfall and relative humidity (ii) mean minimum and maximum temperature

Figure 3.4 Weather parameters throughout 3rd weathering test (Jun 86 2008 until December 2008) (i) mean rainfall and relative humidity (ii) mean minimum and maximum temperature

Figure 3.5 Weather parameters throughout 5th weathering test (Jun 87 2009 until December 2009) (i) mean rainfall and relative humidity (ii) mean minimum and maximum temperature

Figure 4.1 The NBRr particle size and density distribution graf 89

Figure 4.2 The scanning electron microscopy ofNBRr at 30X 90 magnification

Figure 4.3 The size ofNBRr Sl in range (124-360 Jlm) 90

Figure 4.4 The size ofNBRr S2 in range (0.85-15.0 mm) using image 91 analyzer

Figure 4.5 The size ofNBRr S3 in range (I 0-19 em) 91

Figure 4.6 The size ofNBRr captured randomly in smallest size 91

xiii

(71.70 J.lm)

Figure 4.7 FTIR spectrum ofNBRr gloves 92

Figure 5.1 The effects ofNBRv and NBRr on tensile strength of 97 SBRJNBRr and SBR/NBRr blends

Figure 5.2 The effects ofNBRv and NBRr on MlOO ofSBRJNBRv 98 and SBRJNBRr blends

Figure 5.3 The effects ofNBRv and NBRr on hardness of 99 SBR/NBRv and SBR/NBRr blends

Figure 5.4 The effects ofNBRv and NBRr on elongation-at-break, 100 Eb of SBRINBRv and SBRINBRr blends

Figure 5.5 The effects ofNBRv and NBRr on cross-link density of 100 SBR/NBRv and SBR/NBRr blends

Figure 5.6 The effects ofvNBR and rNBR on resilience of 101 SBR/vNBR and SBR/rNBR blends

Figure 5.7 The effects ofNBRv and NBRr on fatigue ofSBR/NBRv 102 and SBR/NBRr blends

Figure 5.8 Scanning electron micrograph of tensile fracture surfaces 104 ofSBR/NBRv blends, (al) 95/5, (b1) 85/15, and (c1) 50150; and SBRINBRr blends, (a2) 95/5, (b2) 85/15 and (c) 50150

Figure 5.9 Scanning electron micrograph of fatigue fracture surface 105 ofSBRINBRv blends, (d1) 95/5, (e1) 85/15, and (fl) 50150; and SBRINBRr blends, (d2) 95/5, (e2) 85/15, and (t2) 50150

Figure 5.10 FTIR spectra of SBRINBRv (R05), SBRJNBRr (R05), 107 SBRINBRv (Rl5), SBR/NBRr (R15), SBRINBRv (R50), SBRINBRr (R50) blends

Figure 5.11 The proposed interaction of SBR and NBR 107

Figure 5.12 TGA thermograms of SBRINBRv (R05), SBR/NBRr 109 (R05), SBRINBRv (R15), SBR/NBRr (R15), SBR/NBRv (R50) and SBR/NBRr (R50) blends

Figure 5.13 DTG thermograms ofSBRINBRv (R05), SBRINBRr 109 (R05), SBR!NBRv (R15), SBR/NBRr (R15), SBR/NBRv (R50) and SBRJNBRr (R50) blends

xiv

Figure 5.14 DSC thermograms ofSBR/NBRv (R05), SBRINBRr Ill (R05), SBRINBRv (R15), SBRINBRr (R15), SBR/NBRv (R50), SBRINBRr (R50) blends

Figure 6.1 The effect of different size ofNBRr and blend ratio on 117 tensile strength of SBR/NBRr blends

Figure 6.2 The effect of different size ofNBRr and blend ratio on 118 fatigue life of SBR/NBRr blends

Figure 6.3 The effect of different size ofNBRr and blend ratio on 119 Ml 00 of SBR/NBRr blends

Figure 6.4 The effect of different size ofNBRr and blend ratio on 119 hardness of SBR/NBRr blends

Figure 6.5 The effect of different size ofNBRr and blend ratio on 120 crosslinking density of SBR/NBRr blends

Figure 6.6 The effect of different size ofNBRr and blend ratio on 121 elongation at break (Eb) of SBR/NBRr blends

Figure 6.7 The effect of different size ofNBRr and blend ratio on 121 resilience of SBR/NBRr blends

Figure 6.8 Effects ofNBRr particle size: (a) Sl, (b) S2, and (c) S3 on 122 SEM tensile fracture surfaces of SBR/NBRr blends at 95/5 blend ratio

Figure 6.9 Effects ofNBRrparticle size: (a) Sl, (b) S2, and (c) S3 on 123 SEM tensile fracture surfaces of SBR/NBRr blends at 85/15 blend ratio

Figure 6.10 Effects ofNBRr particle size: (a) Sl, (b) S2, and (c) S3 on 124 SEM tensile fracture surfaces of SBR/NBRr blends at 50150 blend ratio

Figure 6.11 Effects ofNBRr particle size: (i) Sl(a), S2(a), S3(a); 95/5 125 blend ratio (ii) S 1 (b), S2(b ), S3(b ); 85115 blend ratio,(c)Sl(c),S2(c),S3(c); 50/50 blend ratio on SEM fatigue fracture surfaces of SBR/NBRr blends

Figure 6.12 FTIR spectra of different size NBRr in SBR/NBRr R05 127 and R50 blends

Figure 6.13 TGA thermo grams of SBR/NBRr R05 (S 1 ), SBR/NBRr 129 R05 (S2), SBR/NBRr R05 (S3), SBR/NBRr R50 (Sl), SBR/NBRr R50 (S2) and SBRINBRr R50 (S3) blends

XV

Figure 6.14 DTG thermo grams of SBR/NBRr R05 (S 1 ), SBRINBRr 129 R05 (S2), SBRINBRr R05 (S3), SBRINBRr R50 (S 1 ),SBRINBRr R50 (S2) and SBR/NBRr R50 (S3) blends

Figure 6.15 DSC thermogram of SBR/NBRr blends ofNBRr ranging 131 from 117-334 Jlm (S1), 0.85 -15.0 mm (S2) and 10-19 em (S3) at 95/5 (R05) and 50/50 (R50) blends ratio

Figure 7.1 The effect of blend ratio on tensile strength of SBR/NBRr 137 blends with and without TOR

Figure 7.2 The effect of blend ratio M100 ofSBRINBRr blends with 138 and without TOR

Figure 7.3 The effect of blend ratio on hardness of SBRINBRr blends 138 with and without TOR

Figure 7.4 The effect of blend ratio on crosslinked density of 139 SBR/NBRr blends with and without TOR

Figure 7.5 The effect of blend ratio on elongation at break (Eb) of 140 SBRINBRr blends with and without TOR

Figure 7.6 The effect of blend ratio on resilience of SBRINBRr 141 blends with and without TOR

Figure 7.7 The effect of blend ratio on fatigue life (kc) of SBRINBRr 142 blends with and without TOR

Figure 7.8 SEM micrographs showing tensile fracture surface of 143 SBR/NBRr blends at 95/5 blend ratio (a) and (c) with TOR; (b) and (d) without TOR at 300X and 2.00X magnifications

Figure 7.9 SEM micrographs showing tensile fracture surface of 145 SBRINBRr blends at 50/50 blend ratio (a) and (c) with TOR; (b) and (d) without TOR at 300X and 2.00X magnification

Figure 7.10 Fatigue failure surface SBR/NBRr blends (a) without TOR 146 (b) with TOR at 95/5 blend ratio

Figure 7.11 Fatigue failure surface SBR/NBRr blends (a) without TOR 146 (b) with TOR at 75/25 blend ratio

Figure 7.12 Fatigue failure surface SBRINBRr blends (a) without TOR 147 (b) with TOR at 50/50 blend ratio

Figure 7.13 FTIR analysis of SBR/NBRr blend with and without TOR 148

XVI

Figure 7.14 Propose interactions of SBR and NBRr with the presence 148 of TOR

Figure 7.15 TGA thermograrns ofR05/TOR, R50/TOR, R05 and R50 150

Figure 7.16 DTG thermo grams of SBR/NBRr (R05), SBRINBRr/TOR 151 (R05/TOR), SBR/NBRr (R50) and SBR/NBRr/TOR (R50/TOR)

Figure 7.17 DSC thermograms of SBR, NBRr, SBR/NBRr (R05), 153 SBRINBRr/TOR (R05/TOR) ,SBR/NBRr (R50) and SBRINBRr/TOR (R50/TOR)

Figure 8.1 The tensile strength of SBR/NBRr blends with and without 158 ENR-50

Figure 8.2 The tensile modulus (M100) ofSBRINBRr blends with & 158 without ENR-50

Figure 8.3 The cross-linked density of SBRINBRr blends with & 159 without ENR-50

Figure 8.4 The elongation at break (Eb) of SBRINBRr blends with & 160 without ENR-50

Figure 8.5 The hardness of SBRINBRr blends with and without ENR- 161 50

Figure 8.6 The resilience of SBRINBRr blends with and without 161 ENR-50

Figure 8.7 The fatigue life of SBRINBRr blends with and without 163 ENR-50

Figure 8.8 SEM micrographs showing tensile fracture surface of 164 SBR/NBRr blends at 95/5 blend ratio (a) and (c) with ENR-50; (b) and (d) without ENR-50 at 300X and 5.00X magnifications

Figure 8.9 SEM micrographs showing tensile fracture surface of 165 SBR/NBRr blends at 50/50 blend ratio (a) and (c) with ENR-50; (b) and (d) without ENR-50 at 300X and 5.00X magnification

Figure 8.10 Fatigue failure surfaces of SBRINBRr blends a) without 166 ENR-50 b) with ENR-50 at 95/5 blend ratio

Figure 8.11 Fatigue failure surfaces of SBRINBRr blends a) without 166

xvii

ENR-50 b) with ENR-50 at 50/50 blend ratio

Figure 8.12 FTIR analysis of SBRINBRr blend with and without ENR- 168 50

Figure 8.13 Propose interactions of SBR & NBRr with the presence of 169 ENR-50

Figure 8.14 TGA thermograms ofR05/ENR-50, R50/ENR-50, R05 171 and R50

Figure 8.15 DTG thermo grams of SBRINBRr (R05), 171 SBR/NBRr/ENR-50 (R05/ENR-50), SBRINBRr (R50) and SBR/NBRr/ENR-50 (R50/ENR5Q)

Figure 8.16 DSC thermogram of SBR, NBRr, ENR-50, R05 174 (SBRINBRr blends at 95/5 phr), R05 ENR-50 (SBR/NBRr/ENR-50 at 85/5/1 0), R50 (SBRINBRr blends at 50/50 phr) and R50 ENR-50 (SBRINBRr/ENR50 at 40/50/10 phr)

Figure 9.1 The effects of tensile strength of CB/Sil hybrid fillers 181 filled SBRINBRr blends with and without Si69

Figure 9.2 The effects oftensile modulus (M100) ofCB/Sil hybrid 182 fillers filled SBRINBRr blends with and without Si69

Figure 9.3 The effects oftensile modulus (M300) ofCB/Sil hybrid 182 fillers filled SBRINBRr blends with and without Si69

Figure 9.4 The effects of elongation at break (Eb) of CB/Sil hybrid 183 fillers filled SBRINBRr blends with and without Si69

Figure 9.5 The effects of crosslinked density of CB/Sil hybrid fillers 183 filled SBRINBRr blends with and without Si69

Figure 9.6 The effects of hardness of CB/Sil hybrid fillers filled 185 SBRINBRr blends with and without Si69

Figure 9.7 The effects of resilience of CB/Sil hybrid fillers filled 186 SBRINBRr blends with and without Si69

Figure 9.8 The effect on fatigue life of SBRINBRr blends filled 187 hybrid filler with and without Si69

Figure 9.9 The schematic effects on distribution of CB/Sil hybrid 188 fillers filled SBRINBRr [CB (e), Silica (0)]

Figure 9.10 The tensile fracture surfaces of CB/Sil hybrid fillers filled 189

XVIIJ

SBR/NBRr blends (a) and (b) with Si69, (c) and (d) without Si69 at 40/10 blend ratio

Figure 9.11 The tensile fracture surfaces of CB/Sil hybrid fillers filled 190 SBR/NBRr blends (a) and (b) with Si69, (c) and (d) without Si69 at 20/30 blend ratio

Figure 9.12 The tensile fracture surfaces of CB/Sil hybrid fillers filled 191 SBR/NBRr blends (a) and (b) with Si69, (c) and (d) without Si69 at 0/50 blend ratio

Figure 9.13 Fatigue failure surfaces of SBRINBRr blends filled hybrid 192 filler (a) CB/Sil/Si69 (b) CB/Sil at 40/10 blend ratio

Figure 9.14 Fatigue failure surfaces of SBR/NBRr blends filled hybrid 192 filler (a) CB/Sil/Si69 (b) CB/Sil at 30/20 blend ratio

Figure 9.15 Fatigue failure surfaces of SBRINBRr blends filled hybrid 192 filler (a) CB/SiliSi69 (b) CB/Sil at 10/40 blend ratio

Figure 9.16 FTIR analyses of CB/Sil hybrid fillers filled SBRINBRr 194 blends with and without Si69

Figure 9.17 The proposed interactions of CB/Sil hybrid fillers filled 195 SBRINBRr blends with and without Si69

Figure 9.18 TGA thermo grams of CB/Sil ( 40/1 0), CBiSil (30/20), 196 CB/Sil (10/40), CB/Sil (10/40), CB/Sil/Si6" (40/10), CB/Sil/Si69 (30/20) and CB/Sil/Si69 (1 0/40) hybrid filler filled SBRINBRr blends

Figure 9.19 DTG thermo grams of CB/Sil ( 40/1 0), CB/Sil (30/20), 197 CB/Sil (10/40), CB/Sil (10/40), CB/Sil/Si69 (40/10), CB/Sil/Si69 (30/20) and CB/Sil/Si69 (10/40) hybrid filler filled SBRINBRr blends

Figure 9.20 DSC thermogram of of CB/Sil ( 40/1 0), CB/Sil (30/20), 199 CB/Sil (10/40), CB/Sil (10/40), CB/Sil/Si69 (40/10), CB/Sil/Si69 (30/20) and CB/Sil/Si69 (1 0/40) hybrid filler filled SBRINBRr blends

Figure 10.1 The tensile strength and its retention of SBR/NBRv blends 204 and SBR/NBRr blends after 3 months of natural weathering

Figure 10.2 The tensile strength and its retention of SBR/NBRv blends 205 and SBR/NBRr blends after 6 months of natural weathering

XIX

Figure 10.3 The Eb and its retention of SBRINBRv blends and 206 SBRINBRr blends after 3 months of natural weathering

Figure 10.4 The Eb and its retention of SBRINBRv blends and 206 SBR/NBRr blends after 6 months of natural weathering

Figure 10.5 The MIOO and retention ofSBRINBRv blends and 207 SBRINBRr blends after 3 months of natural weathering

Figure 10.6 The MIOO and its retention ofSBRINBRv blends and 208 SBR/NBRr blends after 6 months of natural weathering

Figure 10.7 SEM of surface a) and b) SBR/NBRv (virgin); c) and d) 209 SBRINBRr (recycled) at 95/5 blend ratio after 3 months natural weathering at 1 OOX and l.OOX magnification

Figure 10.8 SEM of surface a) and b) SBRINBRv (virgin); c) and d) 209 SBR/NBRr (recycled) at 95/5 blend ratio after 6 months natural weathering at 1 OOX and 1.00X magnification

Figure 10.9 SEM of surface a) and b) SBRINBRv (virgin); c) and d) 210 SBRINBRr (recycled) at 85/5 blend ratio after 3 months natural weathering at 1 OOX and l.OOX magnification

Figure 10.10 SEM of surface a) and b) SBRINBRv (virgin); c) and d) 210 SBRINBRr (recycled at 85/15 blend ratio after 6 months natural weathering at 1 OOX and 1.00X magnification

Figure 10.11 SEM of surface a) and b) SBRINBRv (virgin ); c) and d) 211 SBRINBRr (recycled) at 50/50 blend ratio after 3 months natural weathering at 1 OOX and 1.00X magnification

Figure 10.12 SEM of surface a) and b) SBRINBRv (virgin); c) and d) 212 SBRINBRr (recycled) at 50/50 blend ratio after 6 months natural weathering at 1 OOX and 1.00X magnification

Figure 10.13 The tensile strength and its retention of SBR/NBRr blends 213 with different size ofNBRr (S1, S2 and S3) after 3 months of natural weathering

Figure 10.14 The tensile strength and its retention of SBR/NBRr blends 214 with different size ofNBRr (S 1, S2 and S3) after 6 months of natural weathering

Figure 10.15 The Eb and its retention of SBR/NBRr blends with 215 different size ofNBRr (S1, S2 and S3) after 3 months of natural weathering

Figure 10.16 The Eb and its retention of SBRINBRr blends with 216

XX

different size ofNBRr (S1, S2 and S3) after 6 months of natural weathering

Figure 10.17 The M100 and its retention ofSBR/NBRr blends with 217 different size ofNBRr (S1, S2 and S3) after 3 months of natural weathering

Figure 10.18 The M100 and retention ofSBRINBRr blends with 217 different size ofNBRr (S1, S2 and S3) after 6 months of natural weathering

Figure 10.19 SEM micrograph of(a) SBR/NBRv blends; (b) 219 SBRINBRr blends by S 1; (c) SBRINBRr blends by 82; (d) SBRINBRr blends using S3, at 95/5 blend ratio after 3 months natural weathering, at magnification 300X

Figure 10.20 SEM micrograph of(a) SBRINBRv blends; (b) 220 SBR/NBRr blends by S 1; (c) SBR/NBRr blends by S2; d) SBRINBRr blends using S3, at 95/5 blend ratio after 6 months natural weathering, at magnification 300X

Figure 10.21 SEM micrograph of(a) SBRINBRv blends; (b) 221 SBRINBRr blends by S 1; (c) SBR/NBRr blends by S2; (d) SBR/NBRr blends using S3, at 50/50 blend ratio after 3 months natural weathering, at magnification 300X

Figure 10.22 SEM micrograph of(a) SBRINBRv blends; (b) 222 SBR/NBRr blends by S 1; (c) SBR/NBRr blends by S2;

(d) SBR/NBRr blends using S3, at 50/50 blend ratio after 6 months natural weathering, at magnification 300X

Figure 10.23 The tensile strength and its retention of SBRINBRr blends 224 and SBR/NBRr/TOR blends after 3 months of natural weathering

Figure 10.24 The tensile strength and its retention of SBRINBRr blends 224 and SBR/NBRr/TOR blends after 6 months of natural weathering

Figure 10.25 The Eb and retention of SBR/NBRr blends and 225 SBR/NBRr/TOR blends after 3 months of natural weathering

Figure 10.26 The Eb and its retention of SBRINBRr blends and 226 SBR/NBRr/TOR blends after 6 months of natural weathering

Figure 10.27 The MIOO and its retention ofSBR/NBRr blends and 227 SBR/NBRr/TOR blends after 3 months of natural

xxi

weathering

Figure 10.28 The Ml 00 and its retention of SBRJNBRr blends and 227 SBR/NBRr/TOR blends after 6 months of natural weathering

Figure 10.29 SEM micrograph of(a) and (b) SBRJNBRr blends without 229 TOR, (c) and (d) SBRJNBRr blends with TOR at 95/5 blend ratio after 3 months natural weathering, at magnification 300X and l.OOX




Figure 10.33 The tensile strength and its retention of SBR!NBRr blends 232 and SBR/NBRr/ENR-50 blends after 3 months of natural weathering

Figure 10.34 The tensile strength and its retention of SBRJNBRr blends 232 and SBR/NBRr/ENR-50 blends after 6 months of natural weathering

Figure 10.35 The Eb and its retention of SBR!NBRr blends and 233 SBR/NBRr/ENR-50 blends after 3 months of natural weathering

Figure 10.36 The Eb and its retention of SBRJNBRr blends and 234 SBR/NBRr/ENR-50 blends after 6 months of natural weathering

Figure 10.37 The Ml 00 and its retention of SBRJNBRr blends and 235 SBR/NBRr/ENR-50 blends after 3 months of natural weathering

Figure 10.38 The MIOO and its retention ofSBRJNBRr blends and 235 SBR/NBRr/ENR-50 blends after 6 months of natural weathering

XXII

Figure 10.39 SEM micrograph of(a) and (b) SBRINBRr blends without 237 ENR-50, (c) and (d) SBRINBRr blends with ENR-50 at 95/5 blend ratio after 3 months natural weathering, at magnification 300X and l.OOX

Figure 10.40 SEM micrograph of(a) and (b) SBRINBRr blends without 237 ENR-50, (c) and (d) SBR/NBRr blends with ENR-50 at 95/5 blend ratio after 6 months natural weathering, at magnification 300X and l.OOX

Figure 10.41 SEM micrograph of(a) and (b) SBRINBRr blends without 238 ENR-50, (c) and (d) SBRINBRr blends with ENR-50 at 50150 blend ratio after 3 months natural weathering, at magnification 300X and l.OOX

Figure 10.42 SEM micrograph of(a) and (b) SBRINBRr blends without 238 ENR-50, (c) and (d) SBRINBRr blends with ENR-50 at 50150 blend ratio after 6 months natural weathering, at magnification 300X and l.OOX

Figure 10.43 The tensile strength and its retention of of CB/Sil hybrid 240 fillers filled SBRINBRr blends with and without Si69 after 3 months of natural weathering

Figure 10.44 The tensile strength and its retention of of CB/Sil hybrid 340 fillers filled SBRINBRr blends with and without Si69 after 6 months of natural weathering

Figure 10.45 The Eb and its retention of CB/Sil hybrid fillers filled 242 SBRINBRr blends with and without Si69 after 3 months of natural weathering

Figure 10.46 The Eb and its retention of CB/Sil hybrid fillers filled 243 SBRINBRr blends with and without Si69 after 6 months

of natural weathering

Figure 10.47 The Ml 00 and its retention of CB/Sil hybrid fillers filled 243 SBR/NBRr blends with and without Si69 after 3 months.of natural weathering

Figure 10.48 The Ml 00 and its retention of CB/Sil hybrid fillers filled 244 SBRINBRr blends with and without Si69 after 6 months of natural weathering

Figure 10.49 SEM micrograph of CB/Sil hybrid fillers filled SBRINBRr 246 blend (a) and (b) without Si69, (c) and (d) with Si69 at 4011 0 blend ratio after 3 months natural weathering, at magnification 300X and l.OOX

XX111

Figure 10.50 SEM micrograph of CB/Sil hybrid fillers filled SBR/NBRr 246 blend (a) and (b) without Si69, (c) and (d) with Si69 at 40/10 blend ratio after 6 months natural weathering, at magnification 300X and l.OOX

Figure 10.51 SEM micrograph of CB/Sil hybrid fillers filled SBR/NBRr 247 blend (a) and (b) without Si69, (c) and (d) with Si69 at 20/30 blend ratio after 3 months natural weathering, at magnification 300X and l.OOX

Figure 10.52 SEM micrograph of CB/Sil hybrid fillers filled SBRINBRr 248 blend (a) and (b) without Si69, (c) and (d) with Si69 at 20/30 blend ratio after 6 months natural weathering, at magnification 300X and l.OOX

Figure 10.53 SEM micrograph of CB/Sil hybrid fillers filled SBRINBRr 248 blend (a) and (b) without Si69, (c) and (d) with Si69 at 0/50 blend ratio after 3 months natural weathering, at magnification 300X and l.OOX

Figure 10.54 SEM micrograph of CB/Sil hybrid fillers filled SBR/NBRr 249 blend (a) and (b) without Si69, (c) and (d) with Si69 at 0/50 blend ratio after 6 months naturl weathering, at magnification 300X and l.OOX

xxiv

LIST OF SYMBOLS

t2 Scorch time

t9o Cure time

ML Minimum torque

MH Maximum torque

Eb Elongation at break

M100 Stress at 1 00% elongation

kGy Kilo gray

MeV Megaelectron volt

phr Part per hundred of rubber

Tm Melting temperature

Tc Crystallization temperature

Tg Glass transition temperature

MLI+4 Mooney viscosity

Vs Molar volume of the solvent

Vr Volume fraction of the swollen rubber

Qm Total weight swelling

91 The initial angle ( 450)

92 The maximum rebound angle

kg/m3 Relative density

~T Heat build-up

kJ/mol Kilojoule per mol

m:z/g Unit for BET surface area

XXV

LIST OF ABBREVIATIONS

HAF High abrasion furnace

phr Part per hundred rubber

NR Natural rubber

NBR Acrylonitrile butadiene rubber

NBRv Virgin acrylonitrile butadiene rubber

NBRr Recycled acrylonitrile butadiene rubber

SBR Styrene butadiene rubber

W-EPDM Waste ethylene propylene diene monomer

TPEs Thermoplastic elastomers

TPVs Thermoplastic vulcanizates

GRT Ground rubber tire

CB/Sil Carbon black/Silica

ASTM American society for testing and materials

OAN Oil absorption number

COAN Oil absorption number compressed

CBS N-cyclohexyl-2- benzothiazyl sulfenamide

ENR-50 Epoxidized natural rubber (50 mol%)

TOR Trans Polyoctylene Rubber

MDR Monsanto moving die rheometer

IRHD International Rubber Hardness Degree

JIS Japanese Industrial Standard

SEM Scanning electron microscopy

TGA Thermogravimetric analysis

DSC Differential scanning calorimetry . FTIR Fourier transform infrared

ATR Attenuated total reflection

ISO International organization for standardization

Si69 Silane coupling agent

xxvi

PENCIRIAN DAN SIFAT-SIFAT ADUNAN GETAH STIRENA BUTADIENA/GETAH KITAR SEMULA AKRILONITRIL

BUT AD lENA (SBRINBRr)

ABSTRAK

Pengitaran atau penggunaan semula sarung tangan getah kitar semula

akrilonitril-butadiena (NBRr) dengan pencampuran getah sintetik stirena butadiena

(SBR) boleh mewujudkan suatu peluang terhadap altematif produk baru. Keputusan

untuk siri pertama mendapati bahawa adunan getah SBR/NBRr memiliki sifat-sifat

penambahbaikan pada kekuatan tensil, pemanjangan takat putus (Eb) and juga

kelesuan (fatig) terutama mengandungi NBRr tidak melebihi 15 phr berbanding

dengan adunan getah SBR/NBRv. Pada siri kedua pula, didapati adunan getah

SBR/NBRr yang mempunyai saiz NBRr yang paling halus (Sl; 117-334 J..Lm)

menunjukkan interaksi antara-muka yang baik di antara NBRr dan matrik SBR dan

ini ditunjukkan dengan penambahbaikan pada keseluruhan sifat-sifat pematangan

dan mekanikal berbanding dengan adunan SBR/NBRr yang memiliki saiz NBRr

yang lebih besar [0.85-15.0 mm (S2) dan bentuk helaian terns (S3)]. Dengan

pengurangan saiz, pemprosesan akan bertambah efisien (minimum tork rendah, ML)

dan luas permukaan sentuhan akan meningkat di mana akan menyebabkan ikatan

pelekatan-dalaman yang efisien, seterusnya menyumbangkan kepada

penambahbaikan sifat-sifat tertentu. Dalam siri ketiga, penambahan 5 phr getah

trans-polyoctylene (TOR) sebagai agen pembantu pemprosesan telah menambahbaik

pelekatan antara-muka NBRr dengan matrik SBR, seterusnya meningkatkan

keserasian adunan getah SBR/NBRr. Sifat-sifat pematangan seperti masa

pematangan, t90 dan masa skorj, t2 yang pendek serta pemprosesan yang efisien dan

juga sifat-sifat mekanikal/fizikal seperti kekuatan tensil, modulus tensil (M1 00),

XXVIl

kekerasan, kelesuan dan ketumpatan penyambungsilangan adunan getah SBRJNBRr

yang telah dicampurgaul dengan TOR didapati meningkat berbanding adunan getah

SBRJNBRr yang tidak dimasukkan TOR. Sementara itu pada siri keempat,

penambahan 10 phr getah asli terepoksida (ENR-50) juga telah menambahbaik

keserasian adunan getah SBRJNBRr. Secara keseluruhan sifat-sifat pematangan dan

mekanikal adunan getah SBRJNBRr dengan kehadiran ENR-50 memiliki t90 dan tz

yang pendek, pemprosesan yang lebih efisien dan juga peningkatan dalam kekuatan

tensil, kekerasan serta termal yang baik. Pada siri kelima, didapati penggabungan

Si69 dalam adunan getah SBRJNBRr telah menambahbaik sifat-sifat pematangan

seperti masa tgo yang pendek serta pemprosesan yang efisien. Mcutakala

penambahbaikan bagi sifat-sifat mekanikal seperti kekuatan tensil, kelesuan dan

kekerasan pada adunan getah SBRJNBRr dengan CB/Sil/Si69 telah dipengaruhi oleh

darjah ketumpatan sambung-silang. Pada siri keenam, kesan adunan getah

SBRJNBRr terhadap pendedahan kepada pencuacaan semulajadi telah menunjukkan

kemerosotan sifat-sifat terutamanya selepas 6 bulan. Walubagaimanapun,

kebanyakan modifikasi terhadap adunan getah SBRJNBRr telah menunjukkan

variasi penambahbaikkan pada pengekalan sifat-sifat tensil.

XXVIII

CHARACTERIZATION AND PROPERTIES OF STYRENE BUTADIENE RUBBER/RECYCLED ACRYLONITRILE-BUTADIENE RUBBER

(SBRINBRr) BLENDS

ABSTRACT

The recycling or reuse of waste rubber from recycled acrylonitrile-butadiene

rubber glove (recycled NBR glove) by means of blending together with synthetic

rubber styrene butadiene rubber (SBR) can gives an opportunity as an alternative

product. Results in first series indicated that SBR/NBRr blends particularly having

NBRr content up to 15 phr, exhibited improvement in tensile strength, elongation at

break, Eb and fatigue value compared with SBR/NBRv blends. Meanwhile, in

second series SBRINBRr blends with the smallest size ofNBRr particles (Sl, 124-

334 f..tm) showed an improved overall cure characteristics and mechanical properties

compared with all other blend ratios contains of bigger sizes ofNBRr particles [0.85

- 15.0 mm (S2) and direct sheeted form (S3)]. At third series, addition of 5 phr of

trans-polyoctylene rubber (TOR) as compatibilizer improved the adhesion between

NBRr and the SBR matrix, thus improving the compatibility of SBRINBRr blends.

Most of cure characteristics and mechanical properties of compatibilised SBR/NBRr

blends were improved compared with uncompatibilised SBRINBRr blends.

Meanwhile in fourth series, the addition of 1 0 phr of epoxidized natural rubber

(ENR-50) also enhanced the compatibility of the SBRINBRr blends. Overall cure

characteristics and mechanical properties showed that SBRINBRr blends with the

presence of ENR-50 have lower t90, t2 and ML and improved the tensile strength,

hardness and thermal properties. At fifth series, the incorporation of Si69 has

improved the cure characteristics such as lower t90 and ML. Overall improvement on

mechanical properties such as tensile properties, fatigue and hardness of the blends

XXIX

with Si69 were influenced by the degree of crosslinked density as the silica content

is increased. On sixth series the investigation on natural weathering test of all series

of SBR/NBRr blends showed weakening in overall properties particularly after 6

months exposure. However, most of the SBR/NBRr blends with modification

showed better tensile properties with variations of tensile retention.

XXX

CHAPTER 1: INTRODUCTION

1.1 Recycling of waste rubber

1.1.1 An outlook and trend

The waste disposal in the world is a big concern and changing to be ever

increasingly serious with the industry development and the population growth. Over

the last few decades, intensive research and development efforts have been directed

towards finding cost effective and compatible solutions for waste minimization and

utilization (Guo et al., 2010). Recycling of waste rubber has becomes an important

global issue which can solved three major problems; wasting of valuable rubber,

health and environment pollution (Wu and Zhou, 2009). The environment concern

and waste management created by waste rubber and discarded tyres have become

serious in recent years. The global annual production level has reached to about

21.50 million tormes in 2006 (Rubber Industry Report, 2007). Production costs of

polymeric materials obtained from the waste are frequently higher than those of

similar materials made of original polymers. Thus, one has to try to lower the costs

of the material recycling by, e.g., elimination or, at least, reduction of the scale of

the costly process of waste sorting. Rubbers have many applications, ranging from

footwear to automobile tyres, because of their unique mechanical properties such as

good elastic behaviours even at large deformation, and good energy absorbing

capacity. Therefore, improvement of the mechanical properties of the materials

produced from the blends of rubber waste may be accomplished by the application

of suitable compatibilizers, crosslinking additives, and/or electron radiation, which

leads to an increase in the interfacial adhesion of macromolecules of the polymers

forming a given blend. In this way, for example, impact strength of such materials

can be enhanced (Czvikovszky, 2003 and z·enkiewicz and Dzwonkowski, 2007).

The materials obtained from recycling processes should be utilised, if possible, in

areas in which any inferior mechanical properties would play an insignificant role.

Consequently, the mechanical properties of these materials should be thoroughly

examined, but such investigations should be performed with great care because any

deviation from standards and rules relating to both the making of measurements and

the interpretation of results might cause serious errors cz· enkiewicza and Kurcok,

2008).

1.1.2 Malaysia as rubber manufacturer

The Malaysian rubber-based industry has performed well in the last two

decades. Malaysia is currently the worid's ninth largest consumer of all rubber,

following China, USA, Japan, India, Germany, France, South Korea and Russia and

the fifth largest consumer of natural rubber behind China, the USA, Japan and India

(http://www.mrepc.com/industry/). Malaysia is renowned worldwide for its high

quality, competitively priced rubber products. Malaysian rubber products

manufacturers comprise multinationals from various countries including the USA,

Europe and Japan, as well as locally-owned medium and small sized enterprises.

Table 1.1 and 1.2 illustrates the statistical summary of world synthetic rubber and

prices situation from International Rubber Study Group (Rubber Statistical Bulletin,

January-March 2010 edition, International Rubber Study Group). These companies

are able to supply a whole range of rubber products such as medical gloves,

automotive components, beltings and hoses. In other view, Malaysia also is the

leading supplier of examination and surgical gloves, satisfying 45% of the world's

demand. Examination gloves are mainly used in the medical and health care

2

facilities. Furthermore, Malaysia is known as the world's leading supplier of foley

catheters and latex thread (vulcanized rubber thread and cord). Latex thread is

mainly used in the apparel industry as elastic bands and supports. Other important

latex products include condoms, balloons, finger stalls, teats and soothers. Malaysia

has produces a wide range of rubber products (Table 1.3) such as hoses, beltings,

seals, wires and cables for the world market.

Table 1.1 Statistical summary of world synthetic rubber (Rubber Statistical Bulletin, January-March 2010 edition, International Rubber Study Group)

Synthetic 2007 2008 2009 Rubber Production

Year Ql Q2 Q3 Q4 Year Ql Q2 Q3 ('000 tonnes) North 2790 675 655 595 485 2410 410 507 579 America

Latin 684 183 174 155 128 639 114 175 162 America

European 2684 701 686 613 549 2550 474 519 559 Union

Other Europe 1285 356 331 289 207 1182 224 240 281 Africa 71 21 22 19 14 75 14 15 15

Asia/Oceania 5916 1454 1577 1493 1404 5927 1453 1575 1631 TOTAL 13430 3390 3444 3162 2788 12784 2689 3030 3227

Table 1.2 Synthetic rubber price (Rubber Statistical Bulletin, January-March 201 0 edition, International Rubber Study Group)

Synthetic Rubber 2007 2008 . 2009 Prices Year Ql Q2 Q3 Q4 Year Ql Q2 Q3

USA Export Values US Dollar $/tonne 2012 2018 2374 2879 2774 2511 2168 1598 1838

Japan SBR Export Value 'OOOYen/tonne 222 231 243 287 278 260 199 170 180

France, SBR Export Value £/tonne 1483 1493 1566 1798 1951 1702 1628 1441 1522

3

Table 1.3 Malaysia's Export of Selected Rubber Products, 2005 - 2008 (Source: Department of Statistics, Malaysia)

2005 2006 2007 2008 Rubber Products Value Value Value Value

(RM (RM (RM (RM Million) Million) Million) Million)

Gloves, other than surgical gloves 3,793.23 4,624.52 5,095.24 5,991.92 Surgical gloves 706.87 758.39 780.41 916.34 Catheters 647.71 469.92 670.02 285.22 Vulcanized rubber thread and cord 574.20 745.66 720.86 615.48 Wire, cable and other electrical 60.96 86.74 103.04 22.84 conductors Piping and tubing 216.72 223.08 307.60 338.31 Sheath contraceptives 115.78 143.75 151.71 212.50 Belting 55.22 57.92 62.15 59.31 Precured tread of non-cellular rubber 33.69 33.51 38.89 10.88 Cellular rubber lined with textile 24.94 17.23 13.40 6.56 fabric on one side Finger stalls 9.51 9.85 8.67 4.46 Teats & soothers 9.30 12.32 17.36 14.14 Pipe seal rings of unhardened 3.43 2.38 1.53 0.50 vulcanized rubber

1.1.3 Utilization

Recycling rubber waste contributes to a cleaner environment by using

indestructible rubber discards as well as lowering production costs as reclaimed

rubber is cheaper than virgin or natural rubber. Example, Rubplast was set up in

1988 as a joint venture between Malaysian Rubber Development Corporation

(Mardec) and Bombay-based India Coffee and Tea Distribution Company, in . response to the problem of rubber waste (http://www.rubplastmalaysia.net/). The

company processes 500 tonnes of rubber waste each month, turning them into

reclaimed rubber that is mostly exported to rubber product manufacturers abroad. At

the Rubplast factory, rubber glove waste, both rejects from manufacturers as well as

soiled ones from factories, form 3 5% of the waste that is recycled (Fig 1.1 ). Others

4

are scraps from rubber product manufacturers, rubber treads, rubber fleshing (scraps

from tyre manufacturers), nylon-belted tyres, tubes and rubber foam (from cushions

and mattress in Singapore, recyclers are paid S$200 (RM460) for every tonne of

rubber waste recycled because of their effort in minimising waste.

Figure 1.1 Rubber gloves are processed into reclaimed rubber at the Rubplast factory(http:/lthestar.com.my/news/story.asp?file=/2006/6/13/ lifefocus/14433323&sec=lifefocus, Tuesday, June 2006)

In recent years, the practice of recycling has been encouraged and promoted

by increasing awareness in environmental matters and the subsequent desire to save

resources. Together with the relatively high cost of polymers and sometimes high . levels of scrap material generated during manufacture, recycling becomes a viable

and attractive option (Perez et al., 2010). Even the revelation regarding re-utilization

of rubber products in many circumstances, few people still do not realize the

significant of bringing back those waste and become value added materials or

products. In fact, rubber recovery can be a difficult process, however the important

5

of reclaiming or recycling the rubber could be explains as recovered rubber can cost

half that of natural or synthetic rubber; recovered rubber has some properties that are

better than those of virgin rubber; producing rubber from reclaim requires less

energy in the total production process than does virgin material; it is an excellent

way to dispose of unwanted rubber products, which is often difficult; it conserves

non-renewable petroleum products, which are used to produce synthetic rubbers;

recycling activities can generate work in developing countries and many useful

products are derived from reused tyres and other rubber products, if tyres are

incinerated to reclaim embodied energy then they can yield substantial quantities of

useful power. For example, in Australia, some cement factories use waste tyres as a

fuel source. (http://www.practicalaction.org. Practical Action, The Schumacher

Centre for Technology & Development).

1.2 Research background

The utilization of waste rubber powder in polymer matrices provides an

attractive strategy for polymer waste disposal. Addition of scrap or recycled rubber

in the form of either ground waste vulcanizates or reclaim in rubber compounds

gives economic as well as processing advantages. In attempt to lowering the cost of

rubber compounds, the use of cross-linked rubber particles has beneficial effects

such as faster extrusion rate, reduced die swell and better molding ~haracteristics

(Srivanasan et al., 2008).

While most Malaysian glove manufacturers are racing to expand production

and stay ahead in this competitive industry, one concern is that not enough attention

is being given to environmental issues. According to world report from The EDGE,

Malaysian gloves have been used as a global standard benchmark. The conventional

6

glove market, which is dominated by Malaysian manufacturers, global consumption

is about 140 billion pieces of gloves annually and able to produce three billion

pieces a year or even more within three years. One of the major factors that

influence recyclable of rubber gloves is the cost of rubber gloves is still very low.

However, they can be used up to seven times after reconditioning

(http:/ /www.ecoglove.com).

Recycled latex has become a focus of attention compared to reclaimed

rubber due to the lightly cross-linked and high quality nature of rubber hydrocarbon

(George and Rani, 1996, Anandhan et al., 2003). The use of acrylonitrile- butadiene

rubber (NBR) latex in glove production has increased all over the world due to its

excellent resistance to puncture and tears as well as the non-existence of leachable

allergenic proteins, unlike natural rubber latex. Nitrile is an alternative to NR latex.

Nitrile is a synthetic material, and as such, does not have protein. Therefore nitrile

gloves are not likely to cause allergies in people. It interacts to the heat of the

wearer's hand in order to create a snug fit. This is ideal for increased sensitivity.

Nitrile rubber gloves are also soft and resist chemicals much like NR latex.

However, its ability to resist liquids is not as documented as latex is. Nitrile is

appropriate for the auto and industrial fields. It is also used in dental and

pharmaceutical fields (http://www.wisegeek.com/what-are-the-different-types-of

rubber-gloves.htm). Like vinyl, they are less elastic than natural rubber latex (NRL)

but are significantly more durable (Micheal, 2001, Welker and McDowell, 1999).

They feature good physical properties and provide the wearer with good dexterity.

Nitrile gloves are resistant to many chemicals but like other glove types are sensitive

to alcohol degradation. They have been found to be sensitive to ozone degradation

and the elastomers can be somewhat brittle, possessing a higher modulus and greater

7

stiffness than NRL (Graves and Twomey, 2002). While they are abrasion and

puncture-resistant, once breached, they tear easily resulting in breaks where their

varied colours help to identify glove pieces that may end up in food

(http:/ /www.foodsafetymagazine.com/article.asp?id= 13 58&sub=sub 1 ). Unlike other

latex gloves, nitrile gloves have low resistance to friction and are very easy to slide

on. There are a few other reasons that nitrile gloves are more popular than other

latex or vinyl gloves, including a higher degree of flexibility and superior solvent

resistance (http://www. wisegeek.com/what -are-nitrile-gloves.htm ).

Nitrile gloves are currently used in many areas such as the medical field

and, to a greater extent, the food industry, automotive industry, etc. As a result,

significant quantities of discarded gloves are generated worldwide daily. In

Malaysia, the output of nitrile rubber gloves was found abundant. Most of this

material originates from medical, industrial as well as research activities. As a fact,

nitrile rubbt:r is widely use due to great oil resistance, heat and plasticizer and low

gas permeability, high shear strength for structural applications and also its

resilience makes NBR the perfect material for disposable used in lab, cleaning, and

examination gloves

(http://www.gloves.com.my/files/Building%20Blocks%20of'>/o20Nitrile%20Gloves.

pdf). However, after a certain period of time these polymeric materials are not use

and mostly discarded.

In recent year considerable emphasis has been given to utilize either plastics

or rubber waste (such as tyres) in an environment-friendly manner. Through the

rubber recycling technology (the blending of polymer, especially elastomers

together with recycled waste) can meet the performance and processmg

requirements to manufacture a wide range of rubber based products such as road and

8

playground surfaces, recycled rubber flooring, adhesive glues, sporting mats, floats,

marine and automotive parts, and so much more. Many elastomers that have

dissimilar chemical structure are blended to improve processability, performance,

durability, physical properties, and to achieve an economic advantage. Elastomers

with similar polarities and solubility characteristics can be easily combined to

produce a miscible polyblend. In applications where excellent solvent resistance is

not Cf\lciai, it is often desirable to replace acrylonitrile-butadiene rubber (NBR) with

emulsion styrene-butadiene rubber (E-SBR) in order to reduce raw material costs.

Unfortunately, NBR has limited compatibility with non-polar polymers such as

SBR, polybutadiene (BR) and natural rubber (NR). However, the low acrylonitrile

NBR grades can be blended with SBR over the full range of concentrations, without

significant deterioration of mechanical vulcanizate properties. In fact, a number of

these blends are used in several critical applications such as NBR/SBR blends are

used to compensate the volume decrease in oil seal applications (Shield et al., 2001 ).

Therefore, regarding to the present ouput of nitrile glove, perhaps the utilization of

nitrile waste (glove) will be a great deal of interest in the rubber industry about the

development of cost effective techniques to convert waste and used rubber into a

processable form in future.

1.3 Problem statements

It is well known that direct material recycling and reshaping is difficult

because of the irreversible three-dimensional crosslinking of rubber. It means that

they cannot be re-melted or dissolved in organic solvents. The three dimensional

network of sulfur-cured elastomers has the following types of chemical bonds with

their bond dissociation energies (Table 1.4). Many attempts have been made to reuse

9

waste rubbers by reclamation (Benazzouk et al., 2006; Chou et al., 2007),

devulcanization (Jana and Das, 2005; Debapriya et al., 2006; Zhang et al., 2007b),

high pressure and high temperature sintering (Mui et al., 2004), fuel recovery

(Jasmin et al., 2007) and other (Bredberg et al., 2002). Most processes are based on

mechanical shear, heat, and energy input together with a combination of chemicals

such as oils, accelerators, amines, or disulfides to reduce the concentration of sulfur

crosslinks in the vulcanized rubber (Myhre and MacKillop, 2002).

Accordingly, scrap rubber is generally incinerated or discarded in landfills.

These methods cannot be the final solution because they have caused many

problems, such as soil and air pollution. Since most rubber products are sulfur

vulcanized and protectt:d with antidegradants, they produce sulfur and nitrogen

oxides on combustion. These gases are not acceptable in the environment; therefore

the burning of scrap rubber may not be an acceptable solution in the long term

(Myhre and MacKillop, 2002).

Table 1.4 Bond strength of different bonds in rubber network (Rajan et al., 2007)

Type of bond Bond dissociation energy (kJ/mol)

C-C, carbon-carbon bonds 349 C-S-C, sulphur-carbon bonds 302

C-S-S-C, sulphur-sulphur bonds 273 C- Sx- C (x > 3), sulphur-sulphur bonds 256 .

Grinding is the basic step for recycling scrap rubber, and ground rubber (GR)

has been used as the raw material not only for the production of reclaimed rubber

but also for various applications, such as fillers for rubber, fillers for thermoplastic

compounds, and modifiers for asphalt concrete. From economic and environmental

10

points of view, the use of GRas a filler for rubber compounds has more merit than

other methods because it does not need additional processing, reactions, or

treatments, and the chemical nature of the various ingredients in GR can be

maintained (Kim et al., 2007). Meanwhile, the rubber waste is ground to powder and

then devulcanised with the aid of oils and chemicals (a reversal of the process which

hardens rubber latex with the addition of sulphur) to become soft reclaimed rubber,

normally done under high heat in a chamber. However, most of these processes were

either conducted at high temperature, which lead to a higher degradation of the

rubber backbones, or used chemicals as devocalizing agents, which lead to a higher

cost and environmental pollution. Every year large numbers of papers are published

on the recycling of vulcanized rubber products where the rubber powder is used as

filler or blended with virgin rubber or the modified rubber powder is incorporated in

different composite materials (Siddique and Naik, 2004 and Benazzouk et al., 2007).

The most important recycling process currently is to utilize waste rubber as a

very finely ground powder, produced either by ambient temperature mechanical

grinding or by cryogenic shattering. In general, the powder rubber is combined with

virgin elastomer compounds to reduce the costs with the additional advantage of an

improvement of the processing behaviours. However, some loss in physical

properties and performance is observed (Rajan et al., 2007). This factor has

motivated the search for cost effective in situ regeneration or devulcanization of the

scrap rubber to provide recycled material with superior properties.

11

1.4 Research objectives

The aims of these studies were to define the prospective of recycled NBR

glove (NBRr) as a part in styrene butadiene rubber-based blends (SBR/NBRr

blends). Therefore it can be outline as follows;

i) To determine the characteristics and properties of styrene butadiene

rubber/virgin acrylonitrile-butadiene rubber (SBRJNBRv) blends with styrene

butadiene rubber/recycled acrylonitrile-butadiene rubber (SBRJNBRr) blends.

ii) To determine the effects of different size of recycled acrylonitrile-butadiene

rubber and its blend ratio on properties of styrene butadiene rubber/recycled

acrylonitrile-butadiene rubber (SBRJNBRr) blends.

iii) To examine the effects of trans-polyoctylene rubber (TOR) and epoxidized

natural rubber (ENR-50) as a compatibilizer on properties of styrene butadiene

rubber/recycled acrylonitrile-butadiene rubber (SBRJNBRr) blends.

iii) To determine the effects of carbon black/silica (CB/Sil) hybrid filler in the

presence of silane coupling agents (Si69) on properties of styrene butadiene

rubber/recycled acrylonitrile-butadiene rubber (SBRJNBRr) blends.

vi) To study the effects of natural weathering test on tensile properties and

morphology of styrene butadiene rubber/recycled acrylonitrile-butadiene rubber

(SBR/NBRr) blends.

12

CHAPTER 2: LITERATURE REVIEW

2.1 Recycled rubber waste: An approach and utilization

In recent years, the practice of recycling has been encouraged and promoted

by increasing awareness in environmental matters and the subsequent desire to save

resources. Together with the relatively high cost of polymers and sometimes high

levels of scrap material generated during manufacture, recycling becomes a viable

and attractive option. The recycling of scrap material, and mixing with virgin

material, is the most common solution (Perez et al., 201 0). The development of

suitable technology in waste rubber recycling is an important issue faced by the

rubber industry. Lee et al., (2009) studied the effect of physical treatments of waste

rubber powder on the mechanical properties of the revulcanizate. An efficient

grinding machine was designed, used in the powdering of waste rubber tire with

ozone/ultrasonic devulcanization which applied onto the surface of waste tire

powder. As a results, the ozone/ultrasonic treatment was found to be the most

effective treatment to improve the mechanical properties of waste rubber powder

revulcanizate. In almost all commercial applications, the reclaimed rubber is used in

a blend with virgin rubber. Incorporation and dispersion of reclaim rubber into the

virgin rubber plays important roles in product quality and production economy.

Rajan et al. (2006a), observed that reclamation of natural rubber latex based rubber

using 2,20-dibenzamidodiphenyldisulphide as reclaiming agent is an optional

methodology for recycling of waste latex rubber (WLR). Kumar et al. (2007)

revealed a possible techniques that can examine both recycled rubber-virgin rubber

properties; either increasing the effective surface area by reducing the granulate size

or by surface modification of granulates so that it can improve the adhesion between

13

the matrix and granulates. Dierkes et al. (2007) studied the influence of different

amounts of reclaim on the properties of a virgin compound in terms of mechanical

and dynamic viscoelastic properties, crosslink density and distribution and sulfur

distribution between the matrix and the reclaim. They summarized that the

mechanical and viscoelastic properties are affected by the following factors; a)

presence of gel in the reclaim; b) adhesion of the reclaim to the matrix; c) particle

size of the reclaim; d) sulfur distribution between the matrix and reclaim; e)

crosslink density and distribution. The decrease in tensile strength with increasing

concentrations of reclaim with respect to the decrease in the molecular weight of the

sol fraction in the reclaim and the presence of the crosslinked gel. The reclaim

particle acts as an obstacle for stress transmission within a continuous matrix

resulting in an initiation of failure expressed by lower tensile strength. The stress

accumulates on the interface between the reclaimed particle and the matrix and

fracture starts from this point. With increasing concentrations of reclaim, the

concentration of weak spots increases and the tensile strength of the system

decreases. Rajeev and De (2004), has come out with a review on the utilization of

waste rubber and waste plastics for the preparation of thermoplastic elastomers

(TPEs). TPEs based on ground rubber tire (GRT), waste ethylene propylene diene

monomer (W-EPDM) rubber, waste nitrile rubber, recycled rubber, latex waste, and

waste plastics are described with respect to composition and physical. properties. It

was found that part of the rubber phase or plastics phase or both in the rubber

plastics blend can be replaced with corresponding waste polymer for the preparation

of thermoplastic elastomers. In many cases, the materials prepared from waste

polymers show properties comparable to those prepared from fresh polymers.

However, in some cases, the materials prepared from waste rubber or waste plastics

14

cannot be classified as TPEs, as the blend compositions show very low elongation at

break. Modification of the waste polymer or the use of compatibilizers results in

stronger composites. Yun and Isayev (2003) studied about the superior mechanical

properties of ultrasonically recycled EPDM rubber. They found that the tensile

strength of revulcanized EPDM is much higher than that of the original vulcanizates

with elongation at break being practically intact. The investigation on utilization of

powdered EPDM scrap in ~PDM compound by Jacob et al. (2003a), revealed that

processability studies of the compounds show that in the range of selected shear

rates, addition of waste W-EPDM particles improves the extrusion characteristics

like-reduced die swell, better surface smoothness and lesser distortion.

2.1.1 A terminology used for recycling

Recycling can be known as the processes where the reject or scrap rubber is

converted into a reusable material to make new products. Meanwhile, reclaiming is

processes that break down vulcanized rubber by heat in the presence of chemicals or

high-pressure steam. The break down of reject or scrap rubber can be accomplished

by devulcanization (breaking sulfur-sulfur bonds) or by depolymerisation (breaking

polymer chains). The reclaiming procedure consists of two technologies which the

reject or scrap rubber is first chopped into pieces and ground into fine particles

known as crumb. In the second technology, the crumb is subjected to heat in the

presence of chemicals and then followed by intensive friction milling such as

cryogenic. All reclaiming processes require the input of energy. Figure 2.1 show the

summary of reclaiming of rubbers by physical and chemical processes. The two

processes that were most often used were the heater process and the pan process.

The major process at the present time is to utilize the scrap rubber as a very finely

15

ground crumb. In general, the crumb rubber is combined with virgin elastomer

compounds to reduce cost. However, there is some loss in physical properties and

performance. This factor has motivated the search for cost effective in-situ

regeneration or devulcanization of the scrap rubber to provide superior properties.

Reversion is a term used in rubber industry to describe decreases in the mechanical

properties (namely modulus and strength) at the end of the curing period or during

service.

RECLAIMING OF RUBBERS

I I I

I'-------P--hy_s_i_c_al~p_r_o_c_e_ss ______ ~J l~ ______ c_h_e_m_i_ca,l_p_r_o_c_es_s ______ ~ I I

Mechanical By organic disulfides & mercaptans

I Thermo-mechanical

I Cryomechanical

Other ground rubber process i) Dry ambient grinding

ii) Wet or solution grinding

I Microwave method

I Ultrasonic method

I By inorganic compounds

I By miscellaneous chemicals

I Chemical degradation

I Pyrolysis ofwaste rubber

Figure 2.1 The summary of reclaiming of rubbers by physical and chemical processes (Adikari et al., 2000)

16

2.1.2 Grindings and powdered recycled rubber

The simplest approach of rubber recycling is the grinding of vulcanizates and

utilization of the powdered rubber. Powdered rubber is unique as filler because of its

larger size (in the range of microns) and lower modulus, when compared to other

commercial fillers used in the rubber industry. Like other fillers, the polarity (either

the surface functional groups or the polar nature of the polymer) and the structure

(either spongy, chain-like aggregates or free-flowing powder) of ground

vulcanizates affect the physicomechanical properties of ground rubber-filled

vulcanizates. When added to the same base compound (that is, when the

composition of the powdered rubber and the matrix are the same), powdered rubber

can act as an extender to the rubber matrix, with a minimum change in compound

properties. When the compositions of the powdered rubber and the matrix are

different, the factors controlling the loading level for maximum performance include

the compatibility of: elastomeric systems, curing systems, hardness difference, and

tensile strength requirements. The technique of preparation of powdered rubber

greatly influences the particle size and surface topography, which in turn affects the

mechanical properties of the powder-filled compositions. The common methods of

powdering the rubber vulcanizate such as i) ambient grinding (Adhikari et al., 2000),

ii) cryogenic grinding (Liang and Hao, 2000) iii) wet grinding (Klingensmith and

Baranwal, 1998), iv) extrusion (Khait and Torkelson, 1999) and v) .abrasion (Jacob

et al., 2000).

Even the production cost which depends upon liquid nitrogen consumption,

cryogenic grinding is more economical than ambiet grinding (for production of finer

mesh size powders) due to; i) since cryogenically frozen rubber pulverizes more

easily than rubber at ambient temperatures, there is less wear and tear of the

17

machinery, and maintenance costs are significantly reduced and ii) degradation of

the rubber, due to the heat buildup during shearing, is negligible in the cryogenic

grinding method, in contrast to the ambient method.

Besides the composition of the powdered rubber, the other parameters

affecting the performance properties are the particle size and its distribution, shape,

surface topography, and the surface functionalities (that is, the presence of polar

groups on the particle surface). Figure 2.2 illustrates (a) the ultra-fine powdered

rubber (< 10 m) exists as aggregates which break down under shear (b) a typical

abraded particle separated out by the ultrasonic dispersion technique.

Figure 2.2 llustrates (a) the ultra-fine powdered rubber (< 10 m) exists as aggregates which break down under shear (b) a typical abraded particle separated out by the ultrasonic dispersion technique (Jacob et al., 2003a)

2.1.3 Properties of recycled rubber blends based on study case

2.1.3 .1 The influence on rheology

In two series of study involving waste from EPDM, Jacob et al., (2000 and

2003a) highlight that with the addition of EPDM-abraded powder (highly filled and

oil extended) into a gum EPDM rubber compound results in increased Mooney

viscosity but lower high shear viscosity. The drop in viscosity at higher shear rates

18

for the EPDM compound containing EPDM powder with high amount of oil and

carbon black may be due to the wall slippage facilitated by the plasticizer migration.

It is also found that the viscosity increases (at all shear rates) with the increasing

amount of filler present in the powdered rubber. Gibala et al. (1996) studied the cure

and mechanical behaviour of rubber compounds containing ground vulcanizates.

They found that the increase in Mooney viscosity by the addition of ambient ground

powder is more than that by the addition of the same amount of cryoground rubber,

which can be ascribed to the better interaction between the convoluted and rough

surface of the spongy, ambient ground rubber and the matrix.

2.1.3 .2 The influence on curing characteristics

Addition of ground rubber affects the scorch time, optimum cure time, rate

of cure, and state of cure of the rubber compound, depending upon the nature of the

polymer in the matrix and the characteristics of the rubber powder (Gibala et al.,

1996). Ishiaku et al. (2000) studied the effect of convoluted rubber vulcanizate

powder, obtained from the sanding process of polishing rubber balls, on the

properties of NR compound. It was observed that scorch time and cure time decrease

and the tendency toward reversion increases with increasing powder concentration.

The effect of cryoground rubber on properties of NR has been studied by Phadke et

al. (1986). It has also been found that the maximum torque (MH) and the !J. torque

decrease with the addition of ground rubber. The reasons suggested for the

decreased MH value are the plasticizer (acetone extractables) migration from the

ground rubber to the matrix rubber and migration of free sulfur from the matrix

rubber to the cross-linked particles (ground rubber) because there exists a

concentration gradient between the cross-linked and matrix rubber phases.

19

2.1.3.3 The influence on mechanical properties

There are several reports on mechanical properties of ground rubber-filled

rubber vulcanizates. The factors affecting the performance of a vulcanizate

containing powdered rubber are the particle size, hardness, and aging condition of

the precursor rubber article; filler content in the particle; and the particle-matrix

rubber interaction. Ismail et al. (2002a) investigated the comparison properties of

recycle rubber powder (RRP), carbon black and calcium carbonate filled natural

rubber compounds. They found that the tensile strength, tensile modulus, and

hardness increase with increase in CB loading, whereas elongation at break,

resilience, and swelling properties show opposite trend. For RRP and calcium

carbonate filled natural rubber compounds, the tensile strength increases up to

10 phr and starts to deteriorate at higher filler loading. The other properties such as

tensile modulus, hardness, elongation at break, resilience, and swelling percentage

show a small change (increase or decrease) with increase in RRP and calcium

carbonate loading in natural rubber compounds. In other study, the effect of recycled

rubber powder (RRP) on cure characteristics, tensile properties and swelling

behaviour of natural rubber (NR) compounds was investigated in the concentration

range of 0 to 50 phr (Ismail et al., 2002b ).Results indicate that the with increasing

RRP loading also gives natural rubber compounds better resistance towards swelling

and reduces the elongation at break but the tensile stress, M 1 00 ~tress at 100%

elongation) and M300 (stress at 300% elongation), increases slightly. However, the

tensile strength increases up to 10 phr of RRP and then decreases.

Burford and Pittolo (1984) studied the effect of hardness of the rubber

powder (ambient-ground, using shear mill equipped with 1-mm size screen) on the

failure properties of unfilled and carbon black-filled butadiene rubber compounds.

20

Hardness of the powdered rubber has been varied by varying the filler content or the

dosage of the curing agent. It is found that increasing hardness of the rubber powder

causes progressive reduction in tensile strength and elongation at break, but increase

in modulus. Jacob et al. (2003a), studied on utilization of powdered EPDM scrap in

EPDM compound. It was found that the mechanical properties of the vulcanizates

indicate that the optimum loading is 300 phr of recycled EPDM. Although 100 phr

of powdered rubber contributes to a slight increase in modulus (at 100% elongation)

of the vulcanizate, further addition up to 500 phr results in negligible changes only.

At higher elongation (i.e., at 300% elongation) the modulus increases continuously,

implying that the contribution of carbon black content in the particles to the modulus

is evident only at higher strains. The tension set at 100% elongation for the

vulcanizates is low and is independent ofthe powder loading (Table 2.1).

Table 2.1 Effect of powdered rubber (abraded) loading on the mechanical properties of powdered rubber-filled vulcanizates a,b' Jacob et al. (2003a)

Mix Designation Property Wo w1oo wlOO Wsoo

Tensile strength, MPa 1.50 5.66 11.50 9.61 (1.26) (5.65) (10.33) (11.31)

Elcmgation at brenk, '};, 157 411 649 544 (107) (264) (335) (346)

l'vlodulus <lt 100% elongution, tvlPa 1.17 1.35 1.31 1.40 (1.20) ( 1.95) (2.56) (2.86)

Modulus at 300% elongution, tvlPa - 3.86 4.08 4.59 (-) (9.13) (9.51)

Heat build-up (!1TJ at 5lloC, '-'C 1 10 12 13 Hysteresis loss (x10""'), J / m2 0.003 0.007 0.010 0.012 Rebound resilience,'}~, 75 70 67 . 64 Tension set (at 100'~';, elongation), 'V., < 2 2 2 Tear strength, kN/m 8.9 18.8 27.3 26.7

a Values in parentheses stand for the aged specimens (150"C for 72 hr).

"' Formulations contain EPDf\.1, 100; ZnO, 5; stearic acid, 1; TMTD, 1; NIBT, 0.5; •1nd sulfur, 1.5 (in phr), in addition to the powdered EPDM rubber. The subscript in the rnix designation indicates the amount of powdered rubber (in phr) present in the cmnposition.

" Could not be determined· the sample broke.

21

Naskar et al., (2000) studied the effect of GRT of different particle sizes on

the properties of NR compound. It is found that smaller particles contain less

amount of polymer (i.e., NR, BR, SBR) but higher amount of fillers (i.e., carbon

black, silica) and metals (i.e., copper, manganese, iron). Hence, the NR compounds

containing smaller GRT particles show higher physical properties, but poor aging

resistance, because the metals act as prooxidants (Table 2.2).

Table 2;2 Properties ofNR vulcanizates containing 30 Phr ofGRT3 (Naskar et al., 2000)

Physical Properties Gob Gtc G2d

Tensile strength, MPa 14.0 4.2 8.0 (8.8) (2.5) (2.5)

Elongation at break, % 1175 620 860 (770) (360) (400)

Te;u strength, kN /m 28.2 18.5 21.1 (20.3) (10.6) (9.7)

a Values in parentheses stand for the aged samples (lOO<C for 36 hours).

b Compound without GRT. c Particle size 52-72 mesh (300-215 J..Lm) d Particle size 100-150 mesh 050-100 urn)

2.1.4 Acrylonitrile butadiene rubber (NBRr) glove

Nitrile gloves are made from a synthetic polymer exhibiting rubber-like

characteristics when vulcanized. The polymer is manufactured as solids and

emulsion, and can be processed like natural rubber latex. Compared to natural

rubber, softness, feel, modulus, solvent resistance, and tensile and tear-strengths are

designed easily in nitrile production. Unlike natural rubber, which is polyisoprene,

nitrile polymers consist of three monomers: acrylonitrile, butadiene, and any one of

many carboxylic acids. Performance features of the finished glove are controlled

22

through the use of these monomers and their associated formulation ingredients,

such as zinc oxide, sulfur, and process accelerators.

Due to its polar molecular structure, acrylonitrile generally provides

permeation to a variety of solvents and other chemicals. Within nitrile polymers,

acrylonitrile contributes resistance to hydrocarbon oils, fats, and solvents. In

contrast, natural rubber has very poor resistance to these chemicals. Along with

sulfur and chemical accelerators used in the vulcanization process, butadiene

enhances elasticity. In the finished glove, this polymer contributes softness,

flexibility, and rubber-like feel. Interacting with zinc oxide to create ionic bonds

during compound formulation, carboxylic acids contribute tensile strength and

abrasion- and tear resistance in the finished glove. They also enhance solvent

resistance, a characteristic absent in natural rubber because it lacks any carboxyl

functionality. Nitrile has production process advantages over natural rubber, too.

Natural rubber is linear polymer which must be precured to strengthen it before

dipping. In comparison, nitrile polymers are inherently crosslinked so that little or

no precuring is necessary to enhance their strength. The degree of crosslinking is

altered through process conditions and the addition of chemical chain modifiers.

Another important difference between the two materials is the fact that

natural rubber contains proteins, which act as stabilizers. Proteins remain in the

finished glove, and thus, cause allergic reactions in sensitive glove .users. Contrast

this to nitrile, which contains no proteins because it is stabilized with anionic

surfactants. A valuable feature to the semiconductor industry is the ability of nitrile

gloves to more effectively dissipate electrostatic charges. Plus, due to their better

abrasion resistance, they slough off significantly fewer particles, which contaminate

critical manufacturing environments (http://www.techniglove.com/nitrile.html).

23

2.1.5 Synthetic rubber

2.1.5 .1 Styrene butadiene rubber (SBR) (Henderson, 1987, Hofmann, 1989a)

Styrene butadiene rubber (SBR) is a general purpose multitalented synthetic

rubber with many trades name; GRS, Buna S, ASRC, Ameripol, Baytown,

Carbomix, Copo, FR-S, Gentro, Krylene, Krymix, Krynol, Philprene, Plioflex and

Synpol. SBR is much like NR in most of its properties and is the lowest-cost and

highest volume elastomer available. Although the physical properties are slightly

poorer than that NR, SBR is tougher and slightly resistant to heat and flex cracking

and can be readily substituted for natural rubber in many applications with

significant cost savings. The advantages of SBR such as excellent impact strength;

very good resilience, tensile strength, abrasion resistance and flexibility at low

temperatures (Long, 1985a).

Major application characteristics: good physical properties; excellent

abrasion resistance; but sensitive to oil, wastewater and ozone; electrical properties

good, but not outstanding. The elastomer is used widely in pneumatic tires, shoe

heels and soles, gaskets and even chewing gum. It is a commodity material which

competes with natural rubber. Latex (emulsion) SBR is extensively used in coated

papers, being one of the most cost-effective resins to bind pigmented coatings. It is

also used in building applications, as a sealing and binding agent behind renders as

an alternative to PV A, but is more expensive. In the latter application, it offers better

durability, reduced shrinkage and increased flexibility, as well as being resistant to

emulsification in damp conditions (http://en.wikipedia.org/wiki/Styrene-butadiene).

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By NIK NORIMAN BIN ZULKEPLI - Universiti Sains Malaysiaeprints.usm.my/29695/1/Characterization_and_properties_of... · 2016. 2. 17. · NIK NORIMAN BIN ZULKEPLI Thesis submitted in